JPH0466741B2 - - Google Patents

Description

[Detailed Description of the Invention] [Summary] A short test pulse is applied to the solenoid valve drive circuit of an anti-skid device that controls brake hydraulic pressure using a microcomputer to prevent wheels from locking, and its status changes are logically analyzed. By checking, failure diagnosis of the solenoid valve drive circuit can be performed without affecting the actual operation.

[Industrial application field]

TECHNICAL FIELD The present invention relates to an anti-skid device for preventing sideslips in vehicles such as automobiles by braking during running, and more particularly to a fault diagnosis method for a solenoid drive circuit used in the anti-skid device.

[Conventional technology]

If a car is driving on an icy road and the brakes are applied, the wheels will lock and stop rotating, but the wheels will continue to slide on the road and skid, creating a dangerous driving situation. be.

In such cases, a driving method is used in which the brakes are loosened to temporarily release the locked state of the wheels, thereby creating dynamic friction between the tires and the road surface and stabilizing the vehicle.

An anti-skid device is a device for automatically carrying out its operations. FIG. 4 shows a schematic configuration of a general anti-skid device.

In the figure, 1 to 4 are wheels W ₁ to _{W 4} , 5 to 8 are wheel speed sensors, 9 to 12 are electromagnetic valves of the brake hydraulic system, 13 is a microprocessor,
14 is a solenoid valve drive circuit. The operation will be briefly explained below.

The rotational speed of each wheel 1 to 4 is individually detected by wheel speed sensors 9 to 12 and transmitted to a microprocessor 13.

The microprocessor 13 controls the solenoid valve 9 via the solenoid valve drive circuit 14 in order to control the braking state of each wheel brake based on the average value and past value of each wheel speed, control characteristic data, etc.
Opening and closing of 1 to 12 is performed.

FIG. 5 shows a simplified internal configuration of a conventional electromagnetic valve drive circuit 14. As shown in FIG.

In the figure, 15 is a control circuit, 16 and 17
are switching elements Q ₁ and Q _o , 18 and 1
9 represents a solenoid coil within the solenoid valve.

The control circuit 15 in the solenoid valve drive circuit 14 is mainly composed of logic gates, and generates a drive signal having a predetermined timing and pulse width in accordance with commands given to each solenoid valve from the microprocessor 13. is applied to the base of a switching element (eg 16, 17) which drives a solenoid coil (eg 18, 19) which operates the corresponding solenoid valve.

The switching elements 16 and 17 are in a conductive (on) state for a certain period of time when a drive signal is applied to their respective bases, and cause a drive current to flow through the corresponding solenoid coils 18 and 19. When the drive signal disappears, the switching element returns to a non-conducting (off) state, cutting off the drive current flowing through the solenoid coil. These are done relatively quickly.

[Problem that the invention seeks to solve]

Conventional anti-skid devices also have measures to deal with failures such as the drive current supply line from the solenoid valve drive circuit to the solenoid being disconnected, or the switching element being destroyed resulting in a short circuit or disconnection. However, there was a risk that safety would be reduced.

[Means for solving problems]

The present invention provides a diagnostic circuit that checks the operating state of the electromagnetic valve drive circuit for each electromagnetic valve, thereby detecting the occurrence of a failure before the system is activated, and making it possible to take appropriate measures.

For this purpose, the structure of the present invention is an anti-skid device having a solenoid valve drive circuit 14 for driving a solenoid valve for controlling the brake oil pressure of each wheel of a vehicle such as an automobile. Switching elements 16 and 1 for turning on and off the drive current for the solenoid coils 18 and 19 in the valve
A control circuit 15 for turning on and off 7 and a diagnostic circuit 2 for checking whether there is a failure in the solenoid valve drive circuit 14.
0, the diagnostic circuit 20 generates a series of test signals having a shorter pulse width than a normal drive signal, supplies them to the control circuit 15, and controls the switching elements 16, 1.
7 to operate the solenoid coils 18, 19.
is supplied with a drive current that does not reach the normal operating level in time due to its transient characteristics, the resulting state is detected, and the relationship between the detected state and the supplied test signal is It is characterized in that the presence or absence of a failure is determined by detecting whether a predetermined logical relationship holds true.

FIG. 1 shows the basic configuration of the present invention.

In the figure, 14 is a solenoid valve driving circuit, 15 is a control circuit, 16 is a switching element Q ₁ , 17 is a switching element Q _o , 18 and 19 are solenoid coils of the solenoid valve, and 20 is a diagnostic circuit. 21
and 22 are isolation diodes, which detect the operating levels of the switching elements 16 and 17, which are transistors in the illustrated example, based on their collector potentials, and notify the diagnostic circuit 20 as a status signal. do.

The diagnostic circuit 20 generates a test signal, operates the switching elements 16 and 17 via the control circuit 15, and detects the resulting state of the switching element using a status signal via diodes 21 and 22, and performs the test. Normality/abnormality is determined by comparing with the signal.

The test signal has a shorter pulse width than a normal drive signal, and the pulse width of the test signal is shorter than that of a normal drive signal.
However, the drive current flowing through the solenoid coils 18 and 19 cannot reach the operating level over time due to the transient characteristics of the solenoid coils.

[Effect]

In the configuration shown in FIG. 1, in the normal state of the solenoid valve drive circuit 14, when the test signal has a value that turns on the switching elements 16 and 17, the collector potential of the switching element is almost at the ground potential (L level). ), and when the test signal has a value that turns off the switching element, the collector potential of the switching element becomes an electromagnetic potential (high level).

The diodes 21 and 22 transmit an H level state signal to the diagnostic circuit 20 when the corresponding switching elements 16 and 17 are in the off state.

The diagnostic circuit 20 determines whether each switching element correctly responded to the value of the test signal applied to each switching element from the resulting status signal.

Next, an example of diagnostic logic applicable to the present invention will be explained.

Generally, there are n solenoid valves, and the switching elements that drive each solenoid coil are Q ₁ to Q _o
If expressed as
In order to check whether a fault has occurred, a test signal for turning on is applied to all switching elements Q ₁ to Q _o .

At this time, if any one switching element is disconnected, the fault is
It is detected when the state signal taken out from the collector of the switching element shows an H level. That is, if all the status signals are at L level, it is determined to be normal.

If no disconnection failure has occurred, next, remove one switching element and turn on all the others.If the status signal of the excluded switching element is at H level, it is normal, and then at L level. If so, it is determined that a short circuit failure has occurred due to a short circuit in the switching element or a disconnection of the drive current supply line. By sequentially replacing the switching elements that exclude the above-mentioned on-drive, it is possible to determine whether or not there is a short-circuit fault in all of the switching elements.

FIG. 2 shows the above diagnostic logic in a flow consisting of slaps.

〔Example〕

The details of the present invention will be explained below with reference to Examples.

The third is a configuration diagram of one embodiment of the present invention, and shows the internal configuration of an example embodying the diagnostic circuit 20 out of the basic configuration shown in FIG. Accordingly, the general structure of FIG. 1 will be commonly used, and its reference numerals will also be used loosely.

Furthermore, the diagnostic logic in this embodiment is that shown in the flowchart of FIG. 2. Third
The configuration inside the diagnostic circuit 20 newly shown in the figure is as follows.

A test signal generating circuit 23 generates a series of test signals for each electromagnetic valve.

24 is a selector which selects between the drive circuit supplied from the microprocessor in the normal control state (referred to as control mode) and the drive circuit supplied from the microprocessor in the diagnostic state (referred to as diagnostic mode).
The test signal supplied from the test signal generation circuit 23 is switched based on the mode control signal and output to the control circuit 15.

25 is a determination circuit that determines whether the function of the solenoid valve drive circuit is normal or abnormal based on the test signal applied to the switching elements 16, 17, etc. and the status signal indicating the response result in the diagnosis mode. If it is determined that there is an abnormality, an interrupt is issued to the microprocessor.

Each of the circuit elements 25 to 33 is a logic element that implements normal/abnormal judgment logic in hardware,
26, 27, 28 are AND circuits, 29 is an OR circuit,
30 and 31 represent latches, and 32 and 33 represent inverting circuits.

Next, the operation will be explained.

The test signal generation circuit 23 has each A, one bit associated with each of the four solenoid valves to be controlled.
A 4-bit test signal represented by B, C, and D is generated.

The test signal consists of the following five patterns based on the diagnostic logic of FIG. 2, and is generated in this order.

Pattern A B C D 1 1 1 1 0 1 1 1 1 0 1 1 1 1 0 1 1 1 1 0 The value of each bit “1” drives the switching element on, and “0” turns it off. be taken as a thing.

Thus, in the pattern, all four switching elements are turned on, and in the pattern, only one switching element in sequence is turned off, and the rest are driven on.

Such a test signal pattern is closely connected to the logic for determining normality/abnormality, and various patterns other than this example are possible.

The determination circuit 25 determines the presence or absence of a disconnection fault in each switching element based on the test signal pattern, and determines the presence or absence of a short circuit fault based on the pattern.

AND circuit 26 detects the occurrence of a pattern,
It is transmitted to the AND circuit 27. If the status signal is at H level when the pattern is generated, the AND circuit 27 turns on the latch 30 via the OR circuit 29, and notifies the microprocessor of the occurrence of a disconnection failure by an interrupt.

When the pattern does not detect the occurrence of a disconnection fault (disconnection fault), the inverting circuit 32 sets the latch 31 on and remembers that fact.

Next, when the patterns are sequentially generated, the AND circuit 28 detects via the inversion circuit 33 whether the state signal remains at the L level. If the status signal remains at L level, it is determined that a short circuit fault exists and the OR
The latch 30 is set on through the circuit 29 to notify the microprocessor of the occurrence of the fault.

Note that the function of the determination circuit 25 can be realized in exactly the same way by software means.

Furthermore, the status signals can be logically summed for each system of arbitrary electromagnetic valves or for each appropriate control unit, and the unit of diagnosis can also be changed arbitrarily accordingly.

The diagnostic mode is activated immediately after the power is turned on and/or when the vehicle is stopped and other appropriate conditions are satisfied.

〔Effect of the invention〕

According to the present invention, it is possible to accurately detect a failure in the solenoid valve drive circuit or drive current supply line of the anti-skid device and warn the driver, and an appropriate fail-safe mechanism is provided to prevent failures in the event of failure. Actions can be taken automatically to avoid dangerous situations, and safety and driving performance can be improved.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the basic configuration of the present invention, FIG. 2 is a flow diagram of an example of diagnostic logic in the present invention, FIG. 3 is a diagram showing the configuration of an embodiment of the present invention, and FIG. 4 is a general anti-skid device. FIG. 5 is a schematic configuration diagram of a conventional example of a solenoid valve drive circuit. In Fig. 1, 14: Solenoid valve drive circuit, 15: Control circuit, 16, 17: Switching element, 18, 1
9: Solenoid coil of electromagnetic valve, 20: Diagnostic circuit.

Claims (1)

[Claims] 1. Solenoid valve drive circuit 1 that drives a solenoid valve for controlling brake oil pressure of each wheel of a vehicle such as an automobile.
4, the solenoid valve drive circuit 14 includes switching elements 16 and 17 for turning on and off the drive current to the solenoid coils 18 and 19 in each solenoid valve.
a control circuit 15 for turning on and off the solenoid valve drive circuit 14, and a diagnostic circuit 20 for checking whether or not there is a failure in the solenoid valve drive circuit 14.
The diagnostic circuit 20 generates a series of test signals having a shorter pulse width than a normal drive signal and supplies them to the control circuit 15 to control the switching elements 16 and 1.
7 to operate the solenoid coils 18, 19.
is supplied with a drive current that does not reach the normal operating level in time due to its transient characteristics, the resulting state is detected, and the relationship between the detected state and the supplied test signal is A method for diagnosing a solenoid valve drive circuit for an anti-skid device, characterized in that the presence or absence of a failure is determined by detecting whether a predetermined logical relationship holds true.